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Correct extract_if sample equivalent. #135734

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Correct extract_if sample equivalent. #135734

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12 changes: 7 additions & 5 deletions library/alloc/src/vec/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3656,20 +3656,22 @@ impl<T, A: Allocator> Vec<T, A> {
///
/// ```
/// # use std::cmp::min;
/// # let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 6 };
/// # let mut vec = vec![1, 2, 3, 4, 5, 6];
/// # let range = 1..4;
/// # let some_predicate = |x: &mut i32| { *x % 2 == 1 };
/// # let mut vec = vec![0, 1, 2, 3, 4, 5, 6];
/// # let range = 1..5;
/// let mut i = range.start;
/// while i < min(vec.len(), range.end) {
/// let mut end = range.end;
/// while i < min(vec.len(), end) {
/// if some_predicate(&mut vec[i]) {
/// let val = vec.remove(i);
/// end -= 1;
Comment on lines +3663 to +3667
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Isn't this a redundant op? end and vec.len() only ever change at the same time, so it should be possible to do something like while i < vec.len() - diff, where diff is vec.len() - range.end using the original vec.len().

/// // your code here
/// } else {
/// i += 1;
/// }
/// }
///
/// # assert_eq!(vec, vec![1, 4, 5]);
/// # assert_eq!(vec, vec![0, 2, 4, 5, 6]);
Comment on lines +3659 to +3674
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I don't think it needs to exactly match the example below but it should match extract_if, could you add a check against this? Something like:

# let mut vec = vec![...];
# let mut vec2 = vec.clone();
# let mut extracted = vec![];

// ...

        // your code here
#       extracted.push(val);

// ...

# let extracted2 = vec2.extract_if(range, some_predicate).collect::<Vec<_>>();
# assert_eq!(vec, vec2);
# assert_eq!(extracted, extracted2);

/// ```
///
/// But `extract_if` is easier to use. `extract_if` is also more efficient,
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